Please help the newbie, thank you for this forum!

Hello, first of all hello to all at the forum, I bought JGAurora 5 Printer, and would like to learn to do very simple models. I started to learn from youtube yesterday, I have GoggleSketchup that I was learning a bit years ago and I am the most familiar with this but I also learn Autodesk Fusion 360. I cut models with Cura. But I want to start and am stuck here.


I know only how to rescale all model to make everything proportionally bigger.


I own the Brodit mount to my Lexus car, I have holders for iPad and Samsut T1 tablet. Sometimes I just I want to put theremy iPhoneX with an original letter cover. And there is no way to get the right thing to this as I want (that would let me use it with a cover). I have just measured everything and decided to merge 2 projects from thing reverse. The problem is that whatever I try I can only scale the whole project not just its dimension.


The full thing I need to do is to modify the rectangle thing to put into the mount I have in my car (I am attaching photos) the same way as I put in bigger holders for iPad or Samsung tablet. This rectangle thing dimmensions are 50mmx42mm and 3,8mm thin. Then I need any way to make something like an envelope to just put in my iPhone X there. I want to combine somehow 2 projects together, The dimmensions of the rectangle here in the project are not right I do not know for what reason.


1.What can I do to be able to scale the projects in Fusion360? I am attaching the file
2. I am also attaching photos, how can I do it?
3.I am attaching files


Could someone help me please? I will learn more but I even do not know how to start. Maybe someone can help me to resize those dimensions or connect those things together

And all my project files are here https://www.dropbox.com/sh/w266vcmh0...c2Qo-BJca?dl=0