How to filter a character followed by numbers string pattern in PostgreSQL? Back in SQL Server, I use the command below to get the matching string pattern of #1234 from the column called Number
SELECT [m].[Number]
FROM [Boats] AS [m]
WHERE [m].[Number] LIKE N'[#][0-9][0-9][0-9][0-9]'

Now in Postgres, I have tried using the command below, but no luck:
SELECT m.Number
FROM Boats AS m
WHERE m.Number ILIKE '#[0-9][0-9][0-9][0-9]'

Any idea what pattern expression should I use to get the correct filter?
You can use the operator ~ that uses the full power of regular expressions
select *
from (values ('#1234'), ('#3333'), ('#abcd')) as boats (number)
where number ~* '#\d{4}'

A stricter version of the regex would be '^#\d{4}$', so that it matches only strings that start with # then have 4, and only 4 numbers, and then there is the end of the string.