stuck in windows bootcamp / how do i get my firmware password

hello, so i managed to get windows bootcamp, and a friend who did the same and suggested it to me had no issue with switching back and fourth between both windows bootcamp and macos. but i cannot do it. it is asking for what i can gather is my 'firmware password' my only issue is that i got my imac years and years ago now and have no idea what that is or how it was even enabled. i've seen on other discussions that in order to retrieve my firmware password i need to take my imac into an apple service provider but i do not have my original receipt.

is there any other way i can find my firmware password? do i absolutely need the original receipt if i was to theoretically take my imac into an apple service provider?