Will a 4.3 liter engine from 2000 s10 Chevy blazer fit 1997 that also has engine?

No, a 4.3L engine from a 2000 S10 Blazer will likely not be a direct bolt-in replacement for a 1997 S10 Blazer's engine, even if they both have the 4.3L. While the displacement is the same, there were changes to the engine over those years. Things like the computer system (ECM), sensors, and potentially even the mounting points might be different enough to cause compatibility issues. You'd likely need to swap a significant number of components, which would be a very extensive project. It's more trouble than it's worth compared to simply rebuilding or replacing the existing engine.