You should try Velocity for these details which may give you a line for thought.
To start with you can refer:
The links are not accessible. Can you please share the documents if you can access the linls.
This thread dates back to 2012 so it will have become obsolete I guess.
Also there is no simple formula depending on the number of workflows, there are way too many different factors influencing the size of a repository.
The only estimation by rule-of-thumb which I know is the following: create a repository backup file of the repository holding this folder (and no other projects); the size of the backup file will be a hint towards the size of the repository DB.
There is no default/recommended/exact size for the Repository database. It all depends upon your database/table size.
I have recommended the customer to keep the vm same size as the one run in old environment. Thankyou everyone for contributing to the post.