Script help hash table

Hello. Looking for help with constructing a powershell script that will do the following

1. csv file contains list of users (upn)

2. PowerShell script reads all users from csv file (step1.)  does a compare or hash table against users in three specific OU's in AD using (upn). The three specific OU's contain all of our vendor accounts

3. If a match is found, extend account expiration + 90 days

4. if a match is not found write the non matched accounts to a separate .csv file

Thank you very much in advance for any help