The step by step process to read deleted messages on WhatsApp is as follows:
First of all you have to go to your computer or laptop and search wa web plus extension.
After that you will see wa web plus extension on Chrome store, now you have to click on it.
After opening Wa web plus extension, you have to click on Add to chrome on the top right side. After that you have to give permission.
Then you have to come back to WhatsApp again and click on the extension icon given at the top right.
After clicking on the extension icon, you have to click on Wa web plus.
Now you will see some options, in which you have to tick on Restore deleted message.
Now you can go back to a user’s chat and click on their deleted message to see what they sent you.