Creating notation + tablature

I have Dorico Elements version 3.1.10.
Where in this version is ‘Engrave Mode’?

Elements doesn’t have Engrave mode. See the comparison at Compare the Versions of Dorico: Elements & Pro | Steinberg (this is for 3.5 but the same restrictions on SE and Elements apply to 3.1)

Thanks for the info. Now where and how to upgrade?

On the Compare Versions page look out for the red “Get It” button or the red “Buy Now button”. Click any of these and you’ll see a dropdown (probably with Full Version selected). Click the dropdown and select Upgrade from Dorico 2, Dorico 3, Dorico 3.5. There a two of these in the list; one for regular customers and another for educational customers.

I am confused as to which version I need to upgrade to. Is it updates and upgrades for existing customers or the education option, as I am an instrumental teacher?
I bought Dorico Elements 3 full version on 27/04/2020 for £85. And I don’t know which one that was.

If you want to upgrade from Dorico Elements to Dorico Pro and you’re eligible for education pricing, this is the upgrade you need].