You will need a page of thumbnails, and each thumbnail would link to a larger picture.
Just create a folder for your large size pictures, then have the thumbnail page link to that folder.
This is a very common procedure on many web sites.
What's the best way to do this? I have a lot of pics at about 3m pixels and the average file size is between 350 - 600kb. I have Paint shop pro and Adobe programs to make files smaller, but how can the small thumbs turn into a large good quality pic of between say 20 - 30kb ? Some examples I tried showed a tiny pic instead of thumbnail size when I reduced the file size. Would I need to have 2 pics, one small thumbnail and a larger version too.