help!

how to migrate sql from MS sql server to postgresql?
i'd like to tranfer sql schema from MS server
Example:
*******************1*********************************
if exists (select * from sysobjects
where id = object_id(N'[admin].[test]') and
OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [admin].[test]
go
*******************2*********************************
CREATE TABLE [admin].[test] (
[test_name] [char] (50) NOT NULL ,
[test_value] [int] NOT NULL
)

i can only realize part 2. i don't know how to realize part 1.in other words,
i want to know how to check if a table exist in postgresql
*******************2*********************************
create table test(
test_name char (50) not null,
test_value int not null
)

thanks for any advice!!