Will a iPhone 3GS or 4S still work with AT&T Prepaid in 2019?

Just curious cause I'm planning on buying one for various reasons. Will a iPhone 3GS, iPhone 4, or iPhone 4S work with ATT Prepaid in 2019?

Any advice would be welcomed!

Please no rude or unrelated answers!

Why haven't you asked AT&T?

If anyone would know, They would!