Data Access Layer and Custom Tables

I am writing a plugin for nopCommerce 4.50 and have added a custom database table that links a product image to our central image repository.

The table contains two fields:
PictureId int
SharedPictureId int

All I need to do is query this table with a PictureId to return a SharedPictureId value or null.

Is this a case where I want to create a new Entity or just use a Linq query?

Either way, I need to know how to do this through the nopCommerce Service and Data layers. I don't need help with the Linq syntax.

Check existing nopCommerce services code like as GetCustomerByIdAsync method at CustomerService.cs file inside src/libraries /Nop.services/Customer/CustomerService.cs