How do I set a particular quantity for my orders?

On my order form, I have specific prices if they order 5 meals, 7 meals, 10 meals, or 14 meals.

They can choose from 3 dishes. How do I set it so that if they pick the 5-day lunch plan (5 meals total) it will not let them choose over 5 total?

Please feel free to take a look at my form: https://form.jotform.com/nutritionsanctuary/sanctuary-kitchen-order-form

Also, I am wanting to create a subscription for the meal plans as well. Is there any way I can add that option to my existing form without losing my current items?

Just to clarify: when a user selects the 5-day lunch meal plan, they should not order more than 5 total quantities of the sub-products. Is that correct?

If yes, that customization is not possible on the product list field.

You will need to add the products outside the payment field using Quantity Gift registry widgets for each product.

Also, I am wanting to create a subscription for the meal plans as well. Is there any way I can add that option to my existing form without losing my current items?

Sorry, but subscriptions cannot be added to products. The payment type is different and on one payment field, only one payment type can be added.

You would need to create a separate form for subscription payment type to create a recurring subscription - https://www.jotform.com/help/166-how-to-setup-a-recurring-payment-option

How do I add the registry to my current form?
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For the subscription - I want set up something similar to below. The chicken dishes are different price from the beef dish. But I want my customers to be able to mix and match (2 adobo + 2 bulgogi + 1 beef or 3 beef + adobo). Is that possible?
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I also would like to add a coupon code box - is that possible?
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How do I add the registry to my current form?

Here is how you can add the Gift registry widget to the form: https://www.jotform.com/help/252-how-to-add-a-widget-to-your-form

Just search for Gift Registry and you can see the widget in the Form elements tab as explained in the guide above.

The chicken dishes are different price from the beef dish. But I want my customers to be able to mix and match (2 adobo + 2 bulgogi + 1 beef or 3 beef + adobo). Is that possible?

Unfortunately, this is not possible under the subscription payment type. This is possible only when you sell the items as products and enable special pricing on sub-products as you have already done - https://www.jotform.com/help/264-create-sub-products-based-on-a-product-option

I also would like to add a coupon code box - is that possible?

Yes, there is a coupon tab on the payment settings. Here is how you can enable and set up on your payment field: https://www.jotform.com/help/233-how-to-add-coupon-code-to-payment-forms

Let us know if you have any further questions.