Upgrade NOPCommerce from V 3.2 to current version

Neep to upgrade NOP Commerce from 3.2 to current version (4.0 ?) Also need to reinstate current layouts of webstore to new version. We are using the standard NOP clean template of 3.2 We have a very very large database of products Site is up and running and live so we cant have downtime Freelancer must have extensive experience with NOP Commerce Payment in AUD Mention "NOP Experience" when submitting offer so I know you have read and understood all requirements