A couple of these can be had for less than six figures. Do not worry, you do not need scans that large for your slide presentations. File size incorporates all the variables. To place a smaller image into a slide simply calculate the appropriate file size needed. If you want to output film for hardcopy, say a 8x10 print.
All bets are off.
The file size requirements are far more demanding. That places the viewer 3 to 6 times closer than the slide appears to someone in the audience. To place a smaller image into a slide simply calculate the appropriate file size needed. The software that came with your camera may, or may not be capable of this. Photoshop, or another major image editing program will do the job.