While plugin recommendations are essentially out of scope from WPSE … I think it’s ok in this case …
The best solution is to get the WooCommerce Currency Converter premium extension which will set you back 29USD. This means your visitors will get an indication of what they will pay.
Next problem is … Depending on who you have for your payment gateway (Paypal for instance) they will manage the currency conversion and probably charge a different rate. You’ll need to figure that one out with your payment provider.
Why does this matter? because you’ll pay a commission or fees based on the conversion from eg USD to EUR.