Hi @Skullcrusher Vault data is stored in a folder
C:\Users\XXXX\AppData\Roaming\Mozilla\Firefox\Profiles\XXXXXXX.default-release\storage\default\moz-extension+++XXXXX-XXXXX-XXXXX-XXXX-XXX^userContextId=XXXXXX
In this folder search file with number. My file is 709 
See my guide:
If you have more questions. You can contact me on telegram: Telegram: Contact @Luigi_SK