V4 Content Manager shows no record entries for an existing MySQL table

I want to re-create v4 Strapi with an existing MySQL schema (where there are custom tables already containing data entries for v3-to-v4 conversion). I copied and modified api for those existing custom MySQL tables so I can see those tables in the Collection Type list in v4 Content-Type Builder. But when I switch to v4 Content Manager for the existing tables, it shows “0 entries found” in those tables (but actually there are tons of data records in those tables).

How do I get data entries displayed in v4 Content Manager for the existing custom tables? (It is very important for our migration from v3 to v4)