Move from Lean 3 to Lean 4

Stream: lean4

[HinaNarukami]

Recently I'm researching a project using Lean 3, and can't get any use out of it. I want to move the project to Lean 4, but it has a dependency on mathlib3.
Does anyone have experience in moving from Lean 3 (mathlib3) to Lean 4 (mathlib4)?
Thank you a lot.

[Caleb Schultz Kisby]

I haven't personally, but here are the instructions for porting Mathlib code from v. 3 to 4. It includes details about the automated mathport tool, as well as common Lean 3 to 4 fixes (some of the details are specific to Mathlib projects, but most of it appears general). Hopefully someone with more experience using it can chime in.