How do I resize this properly?

I have a picture frame that fits a photo that's sized 10cm x 15cm. The photo I want to put in the frame is on my computer, and I'm not sure how to resize it to fit the measurements. Currently, the photo says 1944 x 2592, but I don't know what it's being measured in. Could someone tell me how to convert this measurement into centimeters, please? Thanks in advance!