If your store does not allow customers to add to cart, instead you want them to contact you when buying product.
You can replace the add to cart button with Make an Enquiry button like the following image.
Go to file Sections > main-product.liquid and find the following code
Replace the found code with the following code
<a href="add your contact page link" class="button button--full-width button--secondary">Make An Enquiry</a>