Install Google Photos on both Samsung and OnePlus phones.

On Samsung, open Google Photos and sign in with your Google account.

Enable Backup & Sync to upload all photos to the cloud.

Wait for all photos to fully sync to your Google account.

On the OnePlus phone, open Google Photos and sign in with the same account.

All your synced photos will appear automatically in the app.

To save them locally, select photos and tap Download.

Alternatively, use OnePlus Clone Phone or Samsung Smart Switch for direct transfer.