How do I merge 6 older saved json files with bookmarks in FF 23.0.1? Thanks

Question

I have 6 old json files from discarded computers to merge with current bookmarks in ff 23.0.1. Looking for a utility that will combine all into one bookmark folder. Thanks in advance.
Application Basics
Name
Firefox
Version
23.0.1
User Agent
Mozilla/5.0 (Windows NT 5.1; rv:23.0) Gecko/20100101 Firefox/23.0
Build Configuration
about:buildconfig
Extensions
Name
Version
Enabled
ID
Adblock Plus
2.3.2
true
{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}
Anti-Banner
13.0.2.600
true
[email protected]
LinkmanFox
8.80.0.0
true
{A81031F3-6CEE-4A19-809F-4E26C1D9C1D1}
Advanced SystemCare Surfing Protection
1.0
false
[email protected]
Content Blocker
13.0.2.600
false
[email protected]
Kaspersky URL Advisor
13.0.2.600
false
[email protected]
Microsoft .NET Framework Assistant
0.0.0
false
{20a82645-c095-46ed-80e3-08825760534b}
Safe Money
13.0.2.600
false
[email protected]
Safe Monitor
2.6.22
false
[email protected]
Virtual Keyboard
13.0.2.600
false
[email protected]
Important Modified Preferences
Name
Value
accessibility.typeaheadfind.flashBar
0
browser.cache.disk.capacity
358400
browser.cache.disk.smart_size.first_run
false
browser.cache.disk.smart_size.use_old_max
false
browser.cache.disk.smart_size_cached_value
358400
browser.places.smartBookmarksVersion
4
browser.search.useDBForOrder
true
browser.startup.homepage_override.buildID
20130814063812
browser.startup.homepage_override.mstone
23.0.1
dom.mozApps.used
true
dom.w3c_touch_events.expose
false
extensions.lastAppVersion
23.0.1
network.cookie.prefsMigrated
true
places.database.lastMaintenance
1376975654
places.history.expiration.transient_current_max_pages
50286
plugin.disable_full_page_plugin_for_types
application/pdf
plugin.importedState
true
privacy.sanitize.migrateFx3Prefs
true
security.disable_button.openCertManager
false
security.OCSP.disable_button.managecrl
false
security.OCSP.enabled
0
storage.vacuum.last.index
0
storage.vacuum.last.places.sqlite
1376975858
user.js Preferences
Your profile folder contains a
user.js file, which includes preferences that were not created by Firefox.
Graphics
Adapter Description
ATI Radeon Xpress 1150 Series
Adapter Drivers
ati2dvag
Adapter RAM
Unknown
Device ID
0x5974
Direct2D Enabled
Blocked for your graphics driver version. Try updating your graphics driver to version 10.6 or newer.
DirectWrite Enabled
false (0.0.0.0)
Driver Date
7-22-2006
Driver Version
8.261.4.0
GPU #2 Active
false
GPU Accelerated Windows
0/1 Basic Blocked for your graphics driver version. Try updating your graphics driver to version 9.6 or newer.
Vendor ID
0x1002
WebGL Renderer
Blocked for your graphics driver version. Try updating your graphics driver to version 9.6 or newer.
AzureCanvasBackend
skia
AzureContentBackend
none
AzureFallbackCanvasBackend
cairo
JavaScript
Incremental GC
true
Accessibility
Activated
false
Prevent Accessibility
0
Library Versions
Expected minimum version
Version in use
NSPR
4.10
4.10
NSS
3.15 Basic ECC
3.15 Basic ECC
NSSSMIME
3.15 Basic ECC
3.15 Basic ECC
NSSSSL
3.15 Basic ECC
3.15 Basic ECC
NSSUTIL
3.15
3.15

Answer 1

By the way, to spell out a previously mentioned approach to gathering all your bookmarks from the old JSON files (https://support.mozilla.org/en-US/questions/968777#answer-470541):
(1) Create a new blank profile
(2) Restore a JSON file (see [[Restore bookmarks from backup or move them to another computer]])
(3) Export the restored bookmarks to an HTML format in a convenient location, with a unique file name (see [[Export Firefox bookmarks to an HTML file to back up or transfer bookmarks]])
(4) Repeat Steps 2 and 3 until you have HTML format exports of all the old bookmarks
(5) Exit Firefox and start up in your normal profile
(6) Import all the HTML files (see [[Import Bookmarks from a HTML file]])
Likely, you will have lots of duplicates, but you will have everything in one place at least.