I think it is best to copy them to an external hard drive first, then you have them "backed up" on the external hard drive if anything goes wrong.
Then plug the EHD into the new PC and copy them off the EHD on to the new PC.
You can use copy and paste, or drag and drop, or even the "Send to" option.
I don't like using "cut and paste" as this removes them from the source and if anything goes wrong with the paste you have lost them.
Copy and paste keeps the originals on the source while doing the copy so you have still got the originals if anything goes wrong.