Changing bit depth

[ritas71524213]

OS Windows 10, PSE15. How can I convert a TIFF or jPeg from a 24 or 32 bit depth to an 8 bit file

[MichelBParis]

You don't convert, you don't need to.

Because it's the same to say 24/32 bits or 8 bits per channel, which is the common usage.

Jpegs are only 8 bits per channel. Tiff or psd can be 16 bits per channel.