Hi, You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• Help -> Troubleshooting Information -> Profile Directory:
• Windows: Show Folder;
• http://kb.mozillazine.org/Profile_folder_-_Firefox

What;s What in the Profile :

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

• bookmarks and history: places.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
• if you only have key3.db then make sure to remove an existing key4.db
• cert9.db (58+) or cert8.db (57 and older) for (intermediate) certificates stored in the Certificate Manager
• if you only have cert8.db then make sure to remove an existing cert9.db
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

RESTORE SESSION FILES (maybe)

• https://www.jeffersonscher.com/res/scrounger_json.html

Data such as "sessions" can get lost when Firefox isn't closed down properly, as when the power to the PC is cut-off. Better now than is was years ago, due to "temporary files" getting created as Firefox is being used, so lesser amounts of data gets lost; but it's not perfect.

I get around that by using an Uninterruptible Power Supply, which allows me to keep using my PC when the power in the neighborhood goes out and gives me time to properly shutdown Firefox and any other application I may have open. I have an APC 600 VA similar to this one: https://www.amazon.com/gp/product/B01FWAZEIU/ref=s9_acsd_top_hd_bw_b3Cto_c_x_1_w?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-3&pf_rd_r=C5559QG76GES471FNQ5S&pf_rd_t=101&pf_rd_p=92dac3d0-4ad8-5e84-b87d-4a65ff94e801&pf_rd_i=764572

https://en.wikipedia.org/wiki/Uninterruptible_power_supply

It also protects against power surges much better than a cheap "surge strip". Where I live it is very common for for the power company to switch connections to my neighborhood; the light "flip off" and comes back on a few seconds later - believe it or not, that just happened here! Thunderstorm for the last couple of hours. Power went out and the UPS started beeping while my PC kept running; 3 seconds later the power came back on.

I have picked up a UPS device for as little as $30 from a clearance table in a Staples store in Feb when they come out with the new models and clearance the old ones to get rid of them. Otherwise that model was like $49.95. I get like 5 years out of them before the battery needs to be replaced.