To export your contacts from Gmail:

1) Navigate to your contacts in GMail

2) Click on "More" and "Export"

 

3) Select the group you'd like to export or "All Contacts"

4) Select "Google csv format" and click on "Export"

This will save the csv file with your contacts to your computer.

If you then want to import your contacts you can find instructions:

a) Here for Gmail

b) Here for Exchange/Outlook

c) Here for Office365