This will work

CREATE OR REPLACE function search_in_table(
owner varchar2,
table_name varchar2,
search_string varchar2)
return varchar2 is
stmt varchar2(32767);
col varchar2(32767);
begin
stmt := 'select ';
for c in (
select column_name
from all_tab_columns
where all_tab_columns.table_name=search_in_table.table_name
and all_tab_columns.owner=search_in_table.owner
and data_type like '%CHAR%' )
loop
stmt := stmt || 'max(case when "' || c.column_name ||
'" LIKE ''' || search_string || ''' then ''' || c.column_name
|| ' ''' || ' else null end) || ';
end loop;
stmt:= stmt||'nvl2(count(*),null,null) from "'||
owner||'"."'||table_name||'"';
execute immediate stmt into col;
return col;
end;
/


select table_name,cols from (
select rownum,
table_name,
search_in_table('SCOTT',table_name,'digit') cols
from all_tables where owner='SCOTT')
where cols is not null;