There is a very strict standard format for screenplays. If you follow it, an 8 minute movie will be 8 pages long. The formatting is different for action and dialog in order to maintain the page/time ratio no matter what the content.

https://screenwriting.io/what-is-standard-screenplay-format/

There are example scripts linked to at the above link.

There is a very strict standard format for screenplays, designed so that each written page of the script will take approximately 1 minute of screen time. The formatting is different for action and dialog in order to maintain the page/time ratio no matter what the content. So, if you follow the format, a script for an 8 minute movie will "magically" be 8 pages long.

https://screenwriting.io/what-is-standard-screenplay-format/

This is not long, so your story should probably be simple and to-the-point rather than detailed and complex. The following link is to a site that posts examples of scripts for short films:

http://www.simplyscripts.com/original-short-scripts.html