There are two kinds of letters: ones without a hole and ones with…I’ll show both:


I like to keep the original, to later fill in the letters…
Select a letter without a hole and press F:

Select one with (a) hole(s) and press X > Limited Dissolve:


Select the inner edges that remained and X > Delete:
Select what’s left of the letter:

And press F to fill:
Then add a Wireframe Modifier, with Boundary:

You can add a Subsurf after that if you want, but you’ll have to check Crease Edges in the Wireframe Modifier!
As you still have the original, you can unhide that…