How to Google form RegEx validation that matches with the "OR" expression in two patterns

I wanted to validate vehicle registration numbers in Sri Lanka in google form.
Here, the registration number is divided into two parts by a "-" sign.
The part to the left of the "-" sign.
Two or three digits. Or two or three English letters. Numbers and letters are never mixed.

The part to the right of the "-" sign.
Always 4 digits.

Below are some example cases.
12-1234, 123-1234, AB-1234, ABC-1234

The following was the most successful regular expression I tried in google form. But here the numbers and letters are mixed in the left part. "|" Sign not working in google form.

[0-9A-Za-z]{2}?[0-9A-Za-z]?\-[0-9]{4}

Below are the other expressions I tried. None of them succeeded properly.

1. ([0-9A-Za-z]{2})$(?[0-9A-Za-z]?)$\-[0-9]{4}
2. ^[0-9]{2,3}$|^[A-Za-z]{2,3}$\-[0-9]{4}
3. [0-9]{2}?[0-9]?-[0-9]{4}
4. [0-9A-Za-z]{2}?[0-9A-Za-z]?\-[0-9]{4}
5. [0-9]{2,3}-[0-9]{4}||[a-zA-Z]{2,3}-[0-9]{4}
6. [0-9]{2,3}-[0-9]{4}|[a-zA-Z]{2,3}-[0-9]{4}
7. [a-zA-Z]{2}?[a-zA-Z]?[0-9]{2}?[0-9]?\-[0-9]{4}
8. ^([a-zA-Z]{2,3}\-[0-9]{4})$
9. ^([0-9]{2,3}\-[0-9]{4})$

can you help me

If you don't want to allow numbers and letters mixed, you will have to use OR and hence you can use following regex,

^(?:\d{2,3}|[a-zA-Z]{2,3})-\d{4}$

Check this out

Here, (?:\d{2,3}|[a-zA-Z]{2,3}) allows either 2 to 3 digits or 2 to 3 letters and rest regex is trivial you already know that part.