With the help of the link How Do I Install/Upgrade/Uninstall an AppExchange App, you can easily understand how to install/upgrade/uninstall the app from the AppExchange.
P.S. Discover Auto Number Helper, the simple way to update Auto Number values in Salesforce. Find it on AppExchange - https://appexchange.salesforce.com/appxListingDetail?listingId=a0N30000000puTcEAI