How Solve Woocommerce WC_Legacy_API

1 – Go to public html files and set wp_debug to true in wp_config.
2 – Go to wp-content > plugins and change the name of the woocommerce plugin’s folder to wocommerce_old.
3 – Check the site. If any other plugins related to WC are causing errors, add _old at the end of their names in the same way.
4 – Go back to Panel. In the warnings section, you can see the warnings from wc-related plugins. If not, download WC from WC’s page or reinstall WC 9.0 from the plugin.
5 – Except for the wc main plugin in item 3, remove the _old expression from the names of the other plugins.

In short, you need to delete the WC and install it again. Even if you do not do it as above, what you need to do is to delete and reinstall it.