How can I get the block "when web1.GotText" & "call web1.PostText text".

I'm trying to connect MySql, I saw many user use these blocks to connect db.
Is there any extensions for this, or others solution?

These blocks are in the Web component, found in the Connectivity section of the Palette.

The tutorial is here

There actually is no need to use an extension for that

To find an extension you can search in the extensions directory here App Inventor Extensions | Pura Vida Apps