Transferring data from Windows 10 to MacBook Pro using Migration Assistant

I am just sitting on the side lines because I can't get past the problem, I don't have a PC passcode when it comes to MA requesting it. So, I don't want to start this process until I know what I will face when I get to that point. Also, MA wants a Mac password, will that password change how I log into Mac? That password allows me to use Mac, my iPhone and my e-mails. So, now do I have to change all those passwords? If I get past this and start the transfer what is the worst that can happen? I don't want to mess up this Mac. I have put all new up to date software on this Mac and so will be transferring data from old versions of the same software. Will this transfer work with new software? Sorry to be such a novice but I want to do this right. Any help greatly appreciated. Oh yes, the data is in Office, photos, and Family Tree Maker. Thanks again

[Re-Titled by Moderator]