How do I jack up 3 sagging floor joist of a conventional foundation ?

Ah Hi, This job calls for a professional, find a contractor that builds houses. Check with Home Advisor or Angie's List. Aloha!

You need a deep concrete pad on the bottom

I had a contractor come and he put cinder blocks and shems. Made a world of difference. It cost $250.

We used a floor jack and piece of wood on top when we put a heavy bakers rack in kitchen. It is still working 18 years later.

Check out this YouTube:

https://www.youtube.com/watch?v=KpQ1rK3fb-8

Try car jacks