Conditional 2

The second conditional is used to imagine present or future situations that are impossible or unlikely in reality.

If we had a garden, we could have a cat.

If I won a lot of money, I'd buy a big house in the country.

I wouldn't worry if I were you.

The structure is usually: if + past simple >> + would + infinitive. 

When if is followed by the verb be, it is grammatically correct to say if I were, if he were, if she were and if it were. However, it is also common to hear these structures with was, especially in the he/she form.

If I were you, I wouldn't mention it.

If she was prime minister, she would invest more money in schools.

He would travel more if he was younger.