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 で世界 が終 わるとしたら、私 の最後 の食事 はお寿司 に間違 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)
だとしたら、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
君 が猫 になったとしたら、どうする?If you became a cat, what would you do?
夏 にイギリスへ行 くとしても、雨 が降 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.