Filter elements by parameter and make them solid

It is a simple question. In fact I though it was really simple, but when I tried I could not make it work. I am sure I am missing something but I do not what.

For example:
<div>I have 4 walls, two walls have Marca(Mark): 30 and the others Marca(Mark):60.</div>
<div>Just I want to convert to solid the wall with 30 value.</div>
<div>Thank you in advance.</div>


Sorry guys for the questions. It jus was stupid.

I made a mistake lacing nodes…

All element of category with list filter…

Thank you any way.