Synced photos not showing in Photos App

I was having an android then switched to iPhone 3 years back. At that time I used iTunes to copy photos from Android to my iPhone.

I used to show around 700+ photos in my Photos App which said "Synced from PC" or something at the top and it was an Album which contained all my photos from my old Android phone.

Today suddenly I see that I cannot see that Album anymore.

I have tried to restart multiple times, Turned on "Shared Photos" option in iCloud settings nothing is working.

How can I restore those photos? Where are they gone?