Payment providers are available on per-country bases as this depends on whether or not they are able to provide their services to a specific country. Stripe is available to a handful of countries; however, if you are not seeing it in your list of available options, then that would indicate you're operating from an unsupported country. If @hasankececi is correct on your location, then you can view a full list of available payment providers for Turkey here.
You can also type in "shopify.com/payment-gateways/countryname" to pull up a list of available payment providers. The URL is case sensitive and requires that you use all lowercase letters. A dash will be required if your country is broken into two segments (i.e. shopify.com/payment-gateways/united-states)
Let me know if you have any questions!