What should look like to be my requirements.txt file?

As base64, random and time are default libraries, your requirements.txt should look like:

python-amazon-paapi
requests

You can have a requirements.txt with or without version specifiers. For example:

[package name] == 0.6.1             # Version Matching. Must be version 0.6.1
[package name] >= 4.1.1             # Minimum version 4.1.1
[package name] != 3.5               # Version Exclusion. Anything except version 3.5
[package name]                      # no specified version
[package name]                      # no specified version