True Kodachrome color processing is essentially no longer available. The original Kodachrome process was unusually complex and was not a practical home process, and the community consensus is that there is no established commercial option for reliable color development now.

There have been reports of experimental one-off services or individuals attempting Kodachrome color development, but with no guarantees. If preserving images is the priority, the practical option is to develop the film as black and white.

Kodachrome can be developed in standard B&W chemistry, and people have reported usable results with developers such as D-76 or even Caffenol. By contrast, C-41 color processing has generally produced disappointing results on Kodachrome.

Because your rolls are old and likely irreplaceable family images, test one roll first rather than all of them at once. If possible, use an experienced lab or darkroom worker for B&W processing and careful scanning. So: color is not realistically available in any dependable way; B&W recovery is the most viable path.