EXERCISES : THE FIRST CONDITIONAL 

http://www.perfect-english-grammar.com/first-conditional-exercise-1.html

http://www.agendaweb.org/verbs/conditional-first-exercises.html

http://www.englishexercises.org/makeagame/viewgame.asp?id=3226

http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/1cond1.htm

https://www.ego4u.com/en/cram-up/grammar/conditional-sentences/type-1/exercises?02