u/Aggravating-Sock5966

Genuine question concerning looking up cards. All of my cards have never been played. Once opened from the packs, light handling and placed in either card sleeves in a binder or stacked with bulk cards. None have ever been played, shuffled or handled much more than from pack to holder.

My question is, how do I assess a cards value if I'm not finding a listing for the same card in similar or greater condition?

I haven't had much interest in assessing values of any until I have decided to part ways with my collection. So any tips or suggestions would help me greatly. Thanks in advance.