These people left the Dems in batches. A chunk did immediately after Obama won the nomination. Another chunk did as soon as he won the presidency. And the final ship sailed once Obama was re-elected, and they now see the Democratic Party as an anti-white hate group.
So, to answer the question, very very few.
We get it, these people vote Republican now. No one is disputing that, and you should give it a rest.
However, MOST of them - especially in states like LA, WV and KY with closed primaries - are still registered Democrats and likely will be into the near future ... the OP is asking what percentage of those voters will vote for which candidate this fall. You could have answered "100% Trump" and actually would have, you know, made sense.