Answer. YOU CAN'T.
One of the cautions I regularly offer (or
@Lazy J Farms Feed & Hay will hop in and mention) is that making feed at home necessarily relies on averages, because you can't assay your feed at home.
Fish meal is a massively moisture reduced, mostly dry ground feed product. It is protein dense because there's little water and often limited fat in it after processing.
Meat is... Meat. That's all you know for certain. Its moisture content is typically in the 75% RANGE. Meaning 100g of generic "meat" is about 75g water, and 25g everything else. If its 80/20 beef, that's potentially 5g of fat, and 20 g of protein. If its 97/3 trimmed skinless checken breast, that's potentially 24g of protein, 1g of fat, both with negligible amounts of other things.
For comparison, "generic" fish meal is about 68% protein after accounting for moisture content, and
one of the most popular fish meals on the market is about 60%.
So, superficially, you are going to need about 3x the weight (or more) of raw "meat" as a fish meal substitute, and you are (most likely) significantly raising the fat content of your final feed.
What meet you start with, how its created, what is qualities are are already unknowable - you can make educated estimates, but no better than that.