I think that your problem isn't that the TYPE
column is LONG but that SEARCH_CONDITION
of user_constraints
is a LONG.
So you can do something similar to the answers in this post, in your case it can look like this:
select count(*)
from
(SELECT XMLTYPE(
DBMS_XMLGEN.GETXML('select SEARCH_CONDITION from user_constraints ')
).extract('//SEARCH_CONDITION/text()').getstringval() srch_cond
from dual)
where srch_cond like '%'g'%'