Update Statement with an inner join

I have data that I've imported into a table in the AS/400 (DB2) from SQL 2000. I need to update a column in a table that previously existed on the AS/400 with the new data I've imported from SQL 2000.

Any idea how to do an update that contains an inner join in DB2?

Here is the problem:

Table1.Column2 (FFIITMAP. FFIHGTH) all records are blank
and I need to update them with the values from Table2.Column2 (cubiscan.CFFIHGTH)
where Table1.Column1(FFIITMAP.FFIITMN) = Table2.Column1(cubiscan.CFFIITMN)

This is how I would do it within SQL 2000
--DB2 Doesn't like the From:Keyword FROM not expected. Valid tokens: <END-OF-STATEMENT>.

Update idsdemo.FFIITMAP
set FFIHGTH = CFFIHGTH
From idsdemo.FFIITMAP
inner join idsdemo.cubiscan on ltrim(rtrim(idsdemo.cubiscan.CFFIITMN)) = ltrim(rtrim(idsdemo.FFIITMAP.FFIITMN))

And these two are ways the internet suggested but still won’t work:

--DB2 Says invalid Tokens
Update idsdemo.FFIITMAP
inner join idsdemo.cubiscan on ltrim(rtrim(idsdemo.cubiscan.CFFIITMN)) = ltrim(rtrim(idsdemo.FFIITMAP.FFIITMN))
set FFIHGTH = CFFIHGTH

--DB2 Says it returns more than one row
Update idsdemo.FFIITMAP
set FFIHGTH =
(select CFFIHGTH from idsdemo.cubiscan
inner join idsdemo.FFIITMAP on ltrim(rtrim(idsdemo.FFIITMAP.FFIITMN)) = ltrim(rtrim(idsdemo.cubiscan.CFFIITMN))
)