Use Courier New, 12-pt, with a fixed Exactly 24-pt per line, first line indent by 1/2". 1" margins on the left and right, 2" margin at top, 1.5" margin at bottom. Header at 1".
You can use Times New Roman if you want, but I prefer Courier New; it is clearer and more like original typewriter type face, which is "traditional".
TITLE (in caps) / Your Name / Page #
Don't worry about a title page. That's easy enough to do later.
Don't worry about how many pages it will be in the final version of the book. That is the publisher's problem. They will choose a font and line spacing to make your book fit their size needs.
The number of Word formatted pages for your book is as long as it takes to tell a good story!
If you really want a good, solid estimate for how many Word pages it will take to create the book you are going for, and feel comfortable about it, just take a book that's formatted the way you hope yours will be, and TRANSCRIBE the first couple of pages. (Type them into your Word formatted template.) That will give you an EXACT estimate of how many Word pages you will need to write.
Technically, you could write the entire book USING a font that's similar to a published book, then AFTERWARDS switch the fonts to Courier and double-line spacing, if you want to "feel" what the book "might" look like published. (That's the joy of Word, you can do that and globally change the entire formatting!) Again, transcribe a few pages from a published book and then play with the fonts, justification, Exact line spacing, and margins until you get it close enough. And afterwards, you can undo all of that and make it have the "correct" format for submission. Whatever works.
Finish the book first. If you're writing it in Word, you can always worry about formatting afterwards.