convert this sql (sql server) to oracle

Select t.username As 'Usurio', tz0id.ip As 'IP', As
       Max(act.dtup) As 'Data'
From tz0id, tz0usr t Inner Join act On (act.usucod = t.usucod and
act.xaction = 0)
Where act.cod = tz0id.cod
Group By t.username, tz0id.ip,
Order By t.username,

    Any help, how to convert this simple SQL to work on oracle, i failed to
use JOIN... any suggestion from oracle experts.