My name is Lilith, I'm on the Social Care team at Shopify.
Depending on the app that you're using to convert currency for your customers, there are options to either have the customer choose their currency or use their IP address to locate them and auto change the currency.
I'm not sure which app you might be using, but I do recommend checking our help guide on Selling in multiple currencies. It's got a great breakdown of how to add the option to your store. There are also some links to the Geolocation app, which is an important part of having the currency change automatically for your customers. There needs to be a locator feature in any app for it to automatically change the currency for the customer.
Additionally, we also have a step-by-step guide on how to add a currency selector to your site as well if you'd prefer that your customers have the option to convert in any currency you offer.
If none of those options appeal to you, you can also opt to use one of these auto-changing apps from our partners instead. Keep in mind that our partners will support those apps, and Shopify will support those apps developed by Shopify.
Let me know how you do with the information above! I'm happy to answer any questions you think of as you work on your business.
You can try Transcy app for currency solution. This app is featured with currency converter that you can use to set up up to 167 currency units for your store. Especially, Transcy can even auto detect the location of your store's visitors to show the friendly currency switcher.
Transcy is available with free plan, so you can try to install 167 currencies without being charged.