Alot of people have already said this but here's my advice.
Work your sprawls.
You aren't going to learn all the wrestling counters and what not, much less be able to effectively use them as good as he does, in time for your fight. Sprawling is much easier to learn and much more effective in amateur.
Work yourself in the cage and practice cutting angles to get off the cage. He might not be able to get you down in the open, but if he can get you up against the cage he will have a much better chance implying his takedowns.
Don't get caught up in the idea that he's coming out there to take you down. Be ready to counter whatever his gameplan is. You come out in a low stance, he fakes a TD, and counters your sprawl.. and your shitted on. Be ready to stand in bang for 3 rounds. His wrestling will probably become his backbone, and if he decides to pull guard, just play defensive. Chances are he is only a blue belt, and you will be able to survive in his guard while inflicting damage. Just be careful, posture up, throw some bombs, and if he attempts anything stand up.
Check out the best e.g. check out the way Junior Dos Santos and Jose Aldo avoid takedowns and get back up once taken down.
These guys in Brazil often have to get by without much wrestling so they are pretty advanced at getting around the TDD VS wrestler problem.
Although helpful, watching UFC fights isn't going to help you THAT much. You really have to understand that almost everything that is happening is a technique followed by a counter. If you don't know the technique, you won't know the counter. Also amateur and pro have different rules which im about to point out in the quote below.
Im not great and all but heres my ideas if you have a grappler keep being in and out and when you go out sideways move so he cant get a hold of your legs change your stances keep him guessing so he has to change the takedown he goes for always watch the kicks incase he catches them but destroying his lead leg would be a clever idea if youre a good at Thai Clinching knee his lead leg quick and get out so he has troubles taking you down
The plum, although useful, isn't very effective in amateur, especially vs a grappler, for 2 reasons.
1. You can't knee to the head. (In most states atleast)
2. Because you can't knee to the head, you have to knee to the body or legs so they have more of an idea where you are going to strike, and when facing a grappler, you don't want them catching that knee and taking you down.
(Knees and elbows to the head are illegal in amateur within most states.)