Elias here with Shopify Support. Thank you for reaching out and that is a great question!
There isn't a way to set a minimum number of products required for the cart or for checkout by default. However, as a way to incentivize your customers to purchase more, one option you can consider is by setting a minimum quantity of items as a condition for your discount codes.
Alternatively, there are third-party apps that can help with setting a minimum purchase requirement, such as Order Limits - MinMaxify or Min&Max Limits by Limitsify. Both of these apps are amazing options that can offer more functionalities that could be useful to you. If you need any help with these apps, you can also reach out to the developers through the contact information found in the Support section of their app's page.
Let me know if any of these options work for you?