There is not an iPad version of the WhatsApp app, so not sure what you were using before. You can access it on Safari and link it to a phone where you could then use a Web App on the iPad that links to the webpage. There are many companion WhatsApp apps that are not made by Meta, and it is possible you had one of those that basically did the same thing as creating a web page. One of those companion apps is called Dual Messenger and if you search "Dual Messenger" in the App Store, you will find many.
Anyway, the official way to run WhatsApp on the iPad is to go to Safari and open the web page. You will see a QRCode that you must scan with a phone to activate the web version on the iPad. For more information on how to use it on the iPad, then it will be their Help site that will offer the most assistance.
https://faq.whatsapp.com