yes u can say that.
however, ur phrase is used for the formal case because u used 数 + number + 次.
for informal cases, we just say 几+百/千/万/十万/百万+次
so u could say, 我已经看过这部电影 几百次了 or 几万次了 or 几亿次了 etc
moreover, u should say 这部电影我已经看过几百次了。 this is totally "chinese-informal-case-style".
for example, ur friend asks u: "你看过这部电影吗？"
u can response like this: “这部电影我已经看过几万次了” or just simply say“我已经看过几万次了”
u see, in this kind of "question-answer" case, if the question is ended by a noun, the answer normally is begun by the same noun to highlight the noun which is asked.