Populating extensionattribute10 for multiple users

I have  4750 active directory accounts with extensionAttribute10 is empty

I would like to populate that field extensionAttribute 10 with firstname.lastname@company.ca

How would I do this in powershell?

 I am working with powershell  2.0 and import-module activedirectory

I would use either a searchbase for the query however my foreach command I do not know what to compose