@malina22 I’m only a beginner but I’ve learnt to build strength and a good frame you need to focus on compounds.
Squats, Bench Press, Deadlifts, Overhead Press and Pull Ups/Rows. These are the main compounds, and the ones you should be doing.
Don’t waste time with too many isolations, save that when you’re experienced. The only isolations you should be doing from the start are Bicep Curls and something for Triceps, like extensions.
So all 5 of those compounds and Bicep and Tricep isolations will probably be the most effective for what you’re looking for.
I wouldn’t know how to split that into a 3 day. 4 would be easier so.
A: Squats, Bench, Pull Ups/Rows. Bicep
B: Deadlift, Shoulder Press, Sit Ups, Triceps.
That’s my routine