Hi
Recently I found out that my image is 300 PPI but I need it to be 300 DPI. How do I change it? Is it even possible to change it in Krita?

Practically speaking, the two are the same.

you are good with what you have. PPI and DPI are used interchangeably and mean the same thing.

Printers print in physical dots (circle blobs) when they printed on paper, so that is why sometimes it is called DPI. Computers work in pixels (squares), so that is where PPI comes from.

Oh really? I must have been mistaken somehow, thank you very much for help!