How to Create SSL-VPN to IPsec VPN using IPsec Tunnel Mode..?

To get helpful responses, you need to describe a little more about your set-up especially the topology. But I would assume you want to let SSL VPN clients connected to the 300E go further across a site-to-site SSL VPN and get to devices there.

As in all vpn situations it's just all about:

1) IPsec Ph2 selectors, if not 0/0<->0/0

2) routing all the way from the source to the destination and vice versa.

3) policies to allow traffic between two interfaces at the 300E and the other FW on the remote end.