How can I click right as using mouse?

I do not believe the right click-style feature found on computers currently works, at all, in iOS.

You can select continuous data in a row or linear fashion using your finger and holding on a piece of text temporarily and then dragging your finger across the screen to highlight/select text/bodies of text.

But there is still NO non-continous/non-contiguous selection in iOS.

Currently, another method that would probably be be useful to you is using the iPad’s own virtual software keyboard trackpad feature.

You can move around the text "I" beam insertion point cursor by bringing up the iPad's software keyboard, do a two finger single tap to turn the entire keyboard area gray colored and into a gigantic trackpad area where you can easily control the position of the text insertion point "I" beam cursor.

You can highlight text and lines/body of text by doing a two finger double tap on the iOS software keyboard.

Then, do a single two finger tap on the keyboard area to fine tune the text selection.

Right now, there is no real right click feature in iOS.

This may/might change in the very near future with the Fall 2019 of iOS 13/iPadOS.

But, currently, this has never been possible to do in iOS.

Best of Luck to You!