Here are the answers with if or when and the correct verb forms:
1 If I get enough money, I'll travel round the world.
2 If it rains this afternoon, we'll stay at home.
3 I'll close the curtains when it gets dark.
4 When I get older, I'll stop playing rugby.
5 You can't go home now, but you can go when the game is finished.
6 Get off the bus quickly when it stops.
7 If you say that again, I'll hit you.
8 When I go to bed tonight, I'll dream about you.
9 If you are in this country next year, I hope you'll come and see us.