On MVJ, under Travel Requirements, then under Pre-Departure Information, read the PDF file. It has info for specific country requirements. This is the section for Turkey ... read the NOTE:
Turkey - In addition to Viking’s vaccination requirement, please ensure you have the following:
1. US/CAN/AU Guests Apply for Turkey’s Electronic Visa, (from a maximum of 90 days to a minimum of 48 hours before departure), found here: https://www.evisa.gov.tr/en/apply/. You will need your passport for the application and will receive your visa via email.
Note: If arriving/departing by air or land, a visa is required in advance. For day visits by sea, a group visa is provided by Viking.
For additional information regarding Turkey’s entry requirements, visit: https://www.tga.gov.tr/fight-against-covid-19-in-turkey/