How to convert SQL store procedure to Postgresql function

hi ,
how can i convert this sql store procedure to postgresql function , i shall be very thankful to you, as i am new to postgresql and i dont know how to handle this kind of store procedure in postgresql
thanks

ALTERPROCEDURE [dbo].[sp_GetUserByID]
      @UserId varchar(50),
      @KBId  varchar(50),
      @phone varchar(50),
      @mhr varchar(50),
      @Distance varchar(50)='',
      @Total varchar(50) output
AS
BEGIN
 
      DECLARE @sql nvarchar(500);
 
 
      if (@Distance='')
            set @Distance = 1
     
      set @sql = 'select mhr_U, begin_U, End_U, areaSize_U, mhr_KB, begin_KB,
End_KB, areaSize_KB, '
      set @sql += ' phone, Distance from vwuserdataSites    where UserId=' + @UserId 
      set @sql += ' and phone>=' + @phone
      set @sql += ' AND KBId=' + @KBId   
      if @mhr<>'All' and ISNULL(@mhr,'')<>''
            set @sql += ' AND mhr_U=''' + @mhr  +''''
      if (@Distance<>'')
            set @sql += ' AND (Distance<=' + Distance + ' or ' + Distance + '=1) '
      set @sql += ' Order by  mhr_U, begin_U'
 
      exec(@sql)
      set @Total = @@ROWCOUNT
END
 
 
 
GO