In general, we use the following rule about estimating the number of prints neatly arranged in a stack: A pack of photo prints that is 1 inch thick is about 100 prints. So, just put your photos in a box (like the one below), measure the number of inches of photos and multiply by 100.
Photo Album Pages
We need four numbers: the dimensions of the page (width and height), the number of album page sides you wish to scan, and the average number of photos per side.
35mm film usually comes/came in rolls of 24 or 36 exposures and so if you have boxes in which the developed slides were returned to you, they will come in boxes that hold 24 or 36 slides. Of course many people have put their slides in special plastic and metal boxes which hold slides. Since each of these boxes hold different quantities of slides, you will just have to count them yourself. Finally, some people have slides in various types of packages. A stack of slides 1 inch high is about 25 slides. Kodak Carousels hold either 80 slides or 140 slides.
Negatives or Positive Transparencies
35mm negatives usually come in strips. Since we scan an entire strip, it is the count of such strips that we need.
Medium format and large format negatives and positive transparencies usually come as individual items. Just count the number of these items.
Video Cassette or Audio Cassette Tapes
The number we need is the count of the individual cassettes.
8mm, Super8mm or 16mm Movie Film
Conversion of Movie Film is charged by the foot. Film reels carry the following amounts of film.