how can i use my backup from a different phone number on a different one?

so to make the long story short: I decided after about a year of changing my sim card that i should change my whatsapp number to my new one, while doing this my whatsapp bugged and all my chats were deleted but i still have a chat backup from directly before this (i made one to be safe while doing so). but when i tried to use it i realised i needed to access my messages from the old phone number to use the backup (i dont have access since the reason i changed my sim card was because i dropped my phone in the sea and the sim stopped working). is there any way to use it? (backup is on google drive)