Q:

How to do simple Substring in Oracle

How do I do this in Oracle Query? this is saying that we want the records which has '1' inleft most position in that column.

AND substring(convert(varchar,TR.MENU_ID_VALUE), 1, 1) = '1'

A:

The convert function function transforms a string from one character set into another. The syntax is convert(<string>, <to character set>, <from character set>)
Also, substring isn't an Oracle function, it's substr.
If you don't need to convert the string then and substr(tr.menu_id_value,1,1) will get you the leftmost character.
If you do want to convert the character set then the full list is available in the documentation, alternatively you can query v$nls_valid_values. For instance if you're converting from WE8MSWIN1252 (Windows code-page 1252) to AL32UTF8 (UTF-8) then your condition would become:
and substr(convert(tr.menu_id_value,'AL32UTF8','WE8MSWIN1252'),1,1) = '1'

From your comment I'm guessing that convert() is the SQL-Server function to convert between data-types. The Oracle equivalent, in this case, would be to_char. Though Oracle will implicitly do the conversion it is always best to use to_char and convert explicitly; giving you:
and substr(to_char(tr.menu_id_value),1,1) = '1'

Incidentally the exact Oracle equivalent is cast(). Strictly speaking, to_char() should be used if you want to use a format model, thus substr(cast tr.menu_id_value as varchar2(10)),1,1) would also give you what you're after assuming the length of tr.menu_id_value was less than or equal to 10.

