You can find a steam link in your purchase email.
If you can't find the email, you can ask itch to resend it.
https://itch.io/docs/buying/already-bought
Unfortunately, the field is not there. Even if I request the link again via the email.
Did you purchase the game on itch or claim it with patreon tier?
If you were claiming the game on itch with free key or patreon tier, it won't provide a steam key.
I bought it here: ”In order to download this game you must purchase it at or above the minimum price of $5.95 USD. Your purchase comes with a Steam key."