How to get value of variable entered from user input?

You'll need to use locals()[Choose_Item] if you want to choose a variable whose name is what the user produced.

A more conventional way to do this, though, is to use a dictionary:

items = {
    'Item1': 'bill',
    'Item2': 'cows',
    'Item3': 'abcdef',
}

... and then the value you want is items[Choose_Item].

This seems like what you're looking for:

Choose_Item = eval(input("Select your item:  "))

This probably isn't the best strategy, though, because a typo or a malicious user can easily crash your code, overload your system, or do any other kind of nasty stuff they like. For this particular case, a better approach might be

items = {'item1': 'bill', 'item2': 'cows', 'item3': 'abcdef'}
choice = input("Select your item: ")
if choice in items:
    the_choice = items[choice]
else:
    print("Uh oh, I don't know about that item")