This is the answer:

Example of writing separate archieves to tape:

mt -f /dev/nst0 rew
tar cf /dev/nst0 dir1/*.img
tar cf /dev/nst0 dir2/*.img
tar cf /dev/nst0 dir3/*.img
tar cf /dev/nst0 dir4/*.img

Example of retrieving separate archieves from tape:

cd mynewdir>
mt -f /dev/nst0 rew
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/nst0 fsf 1
tar xf /dev/nst0
mt -f /dev/st0 rewind

Thanks for your help, i'm really apreciate