TLDR;
Republicans: 302
Democrats: 220
Swing: 16
Trump would only need 270 electors to win, so he wins uncontested.
This is an interesting thought experiment. Keep in mind, this assumes elections are held this way. They may not be. Also worth noting is that this assumes legislatures appoint all electors to the same party and don't do some kind of weird split.
This kind of question is hard to answer, specifically because there are some legislatures that are "purple," or there is no clear part winner. I have called these S for swing states. My approach is to ignore these for now and deal with them later if I have to.
I should also mention that Washington DC gets 3 electors. Since I don't know how these would be distributed--especially in this type of scenario--I'll label is as "swing" too and come back to it if I need to.
With that said, using this list from Wikipedia, we get the legislatures. And with this list, we get the electors. Putting them together, we get this really long table:
State, Legislature Electors
District of Columbia S 3
Alabama R 9
Alaska S 3
Arizona R 11
Arkansas R 6
California D 55
Colorado D 9
Connecticut D 7
Delaware D 3
Florida R 29
Georgia R 16
Hawaii D 4
Idaho R 4
Illinois D 20
Indiana R 11
Iowa R 6
Kansas R 6
Kentucky R 8
Louisiana R 8
Maine D 4
Maryland D 10
Massachusetts D 11
Michigan R 16
Minnesota S 10
Mississippi R 6
Missouri R 10
Montana R 3
Nebraska R 5
Nevada D 6
New Hampshire D 4
New Jersey D 14
New Mexico D 5
New York D 29
North Carolina R 15
North Dakota R 3
Ohio R 18
Oklahoma R 7
Oregon D 7
Pennsylvania R 20
Rhode Island D 4
South Carolina R 9
South Dakota R 3
Tennessee R 11
Texas R 38
Utah R 6
Vermont D 3
Virginia D 13
Washington D 12
West Virginia R 5
Wisconsin R 10
Wyoming R 3
Now, all we have to do is add them up. We get this result:
Republicans: 302
Democrats: 220
Swing: 16
A party needs 270 electors to win. The Republicans (and, by extension, Trump), have well over that, into the 300s. Thus, we don't even have to worry about the 16 "swing" ones. There is already a winner here: the Republicans (Trump).
Keep in mind, this assumes that the state legislatures do appoint the electors, and that everything goes along party lines. A real scenario like this might end up a lot more complicated and is unlikely to happen (at least, certainly this cleanly).