Open Google Drive on your computer or phone
Download the photos from Drive to your device
Open Google Photos
Upload the downloaded photos to Google Photos
On computer, drag and drop the photos into photos.google.com
On phone, use the Google Photos app and tap the upload option
If the photos are in a Google Drive folder, select them all before downloading
Make sure you are signed into the same Google account in both Drive and Photos
Check that the photos appear in Google Photos after upload
Delete the copies from Drive only if you no longer need them there