If the world was ending [としたら]

We can use としたら to  talk about hypothetical situations.

もし今日きょう世界せかいわるとしたらわたし最後さいご食事しょくじはお寿司すし間違まちがいない。

If the world was going to end today, My last meal would be definitely by sushi.

Structure

するとしたら、したとしたら (Verb casual)

としたら、だったとしたら (noun +だ)

You can replace としたら withとすれば without changing the meaning although, according to my grammar books, としたら is slightly more casual. We must also be careful to not mix this up with ようとしたら (the violational form of the verb) which means as I was about to do.

Examples

もしきみねこになったとしたら、どうする?

If you became a cat, what would you do?

なつにイギリスへくとしてもあめるでしょ。

Even supposing we went to England in the summer, It would still rain, wouldn’t it?

In the last example we are using しても to give an even if meaning to the sentence.