GameMaker has an easy way to do this, you should look into views. You only need one view, set it's width and height to 64x64 and set it's port to whatever size you wish (such as 512x512) although usually it'd be the same size as your window. You can set up views in the room editor. Make sure interpolation is off in the Global Game Settings and it should scale nicely. :)
Viewing post in 64x64 , or 128x128 scaled?
I used to work for YoYo Games, so I know my way around GameMaker! If you need more help on this you'd be better off searching or asking on the GMC https://forum.yoyogames.com/index.php. In most cases the manual will have good information and examples as well, particularly on views.