See if this is what you're looking forIn Paint, open up the file.
In the "Home" tab click "Rotate" > "Rotate Left 90 degrees"
Go to File > Page Setup
Make sure Size is Letter
Make sure orientation is Portrait
Make sure to have at least .5 margin in all boxes here
Leave Centering empty
Set "Fit To" to 3 by 3 pages
(At this stage you can see what normal size the picture would print to if you print it to size. Just choose "Adjust To:" & type in 100 % normal size. You'll see the image fits on 2 x 2 sheets of paper. Too small."
Hit "Ok"
Choose File > Print Preview
Scroll page by page to make sure it's what you want.
Close out Print Preview when you're happy.
Print like normal
If you're still not sure, don't waste your color ink. Print a black and white copy and see how it looks. If you're happy, print in color.
I suggest using card stock paper instead of regular paper for more durable and better quality. You can also use photo specific paper.
If you do it at the store they should be able to do it correctly. You might have to offer some friendly guidance.
IMPORTANT NOTE - I haven't printed any of the boards on this forum so I can't vouch whether they print to a size appropriate to miniature base scale. I haven't even tried. I only just made a quick attempt because of your post and from what I've seen things might not print precisely to size. However, that is one way to print images to a poster-sized format. I would open the image into Paint first and delete a lot of its central area with the Eraser tool leaving only a bit of its outer border / edge as well as maybe one room so you don't waste ink. Then convert it to black and white and save that new image, and lastly print that as explained above, and see what the size of a room looks like and the size of the whole board.
Unless you specify your version I'm going by the US rules.
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