Just go through this:
These instructions apply to Macs runningmacOS Catalina (10.15)and up.
Begin by connecting your iPhone to your Mac.
This can be done via the cable that came with your iPhone or over Wi-Fi.

You may be prompted to “trust” the iPhone to sync with the computer.
If so, follow the instructions on the iPhone.
Open anew Finder window.

In the left-hand sidebar, click your iPhone.
Check the box next toSync photos to your rig from:to enable syncing.
In most cases, this will be the pre-installedPhotosapp.

Choose your sync controls.
you’ve got the option to choose to syncAll photos and albumsorSelected Albums.
If you choose Selected Albums, check the ones you want to sync in the box at the bottom.

you could also choose to sync favorite photos and to videos.
If iTunes doesn’t open automatically, open it.
In iTunes, nudge the iPhone icon just beneath the playback controls in the top left corner.

In the left-hand sidebar, clickPhotos.
Check the box next toSync photosto enable syncing.
In the drop down, choose the program that contains the photos you want to sync to your iPhone.

This should be the pre-installedWindowsPhotosapp.
Choose your sync controls.
you could syncAll photos and albumsorSelected Albums.

If you choose Selected Albums, check the ones you want to sync.
For either option, you’re able to also sync favorite photos and to videos.
When you’re done, clickApplyto preserve your prefs and transfer photos from your PC to your iPhone.

If the transfer doesn’t start right away, clickSyncat the bottom right to start transferring photos.
Here’s how:
On your iPhone, tapSettings.
Tap your name at the top of the screen.

Move theiCloud Photosslider to on/green.
When you do this, photos will sync from your iCloud account to your iPhone.
How long this takes depends on how many photos and videos you have and how large the files are.

Once they upload to iCloud, they’ll automatically download to your iPhone.
It’s that simple!