If you are looking to upgrade WooCommerce with latest version, then you need to follow the below points. Woo Commerce is a open source for e Commerce store which have whole functionality and already build-in ecommerce system, which take months in core PHP or other programming language.
WooCommerce has own templates files which generate front end design and can be modified as per business development need. When someone planning to upgrade version then they need to keep some points in the mind otherwise website losts the custom work and default WooCommerce structure will applied.
1. Create a staging version of live website.
2. Enabled WP_DEBUG_LOG to check error.
3. WooCommerce custom work should be in wordpress theme folder.
4. Need database backup
5. Now download latest woo commerce zip file from its website.
6. Replace with old woocommerce file to latest version.
7. Now go into the back-end and click on woocommerce setting option or at the top notification panel you will get upgrade woo-commerce database notification button, run it.
8. Now check front-end and back-end for testing purpose. if WP_debug_log is enabled and error will come you will get in log.
9. In any case log you find any deprecated in template file in woocommerce in theme folder of wordpress, change it otherwise your custom changes will not effect after woocomerce upgradition.