Where is the electrician . . .

I presume these are LED lights.

This will work. There's a slight chance you may need two with 300 total lights. And Menards has related product, extension cables, Y cables, etc. You'll have to "interface" the transformers output to the strands connection.

There's lower price versions to be had on eBay ...

If your electrically adventurous, you can use a variable output regulator. Two or three variable output regulator modules would allow you dial in the brightness for the connected LED strands. Each regulator could handle 2, possibly three strands (we don't have specs on the LEDs themselves).

They're about $2 each on eBay or Aliexpress (3+ weeks ship time). You would need a 12 V "brick" (looks like a laptop power supply and a spare laptop supply would suffice for this application). Or you could use a spare conventional train transformer's accessory output to drive the the regulator modules.

They look like this: