The find button text is most easily changed via the WPSLP Experience add on. or the MYSLP Professional or Enterprise  level plan

Click the Settings tab.

Scroll down to the Search Labels group.

Look for “Find Button” under the sub-group.

Enter the new text you want to see in the button.

Click save.

Your new text will appear on the search form.

 WPSLP do it yourself Add On That Support This Feature

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 The Experience Add On