Easy way to exchange all .tif with .png textures in the models?

Hey
I had a longer break in unity, so sorry for the maybe stupid question. My boss asked me to change the textures, normals etc. from .tif to .png, so far no problem. Over 500 models are effected though (I have them all in a showcase scene), which I would now need to assign 1200 textures to by hand again. The names are still the same, only the format changed. Is their a script or anything that could fix the problem before I start assigning every single one by hand? It would take ages with heightmaps etc.

Thank you all in advance and have a nice day.
- Vivian

 

Doesn't Unity compress all texture with for example ETC so they all ends up the same? How about changing one file first to see how much of a difference it makes in quality, or compression?