convert png to jpg and saved it in c:\mydir\

[baka]

if this is about compression, webp is the today standard for that.
webp is both lossy and lossless depending on your needs.

so png > webp lossless to make it around 60% of its size
or png > webp lossy that is even smaller (depends on quality)

the only reason to use jpeg is for some old program that can not handle webp or png.
otherwise jpeg is obsolete for most cases, since it lossy (destroys the picture) and less compression than webp.

speed-wise, jpeg is fast to load, png takes more time and webp even worse, but should not impact much with new computers.