Hi
Assume that you have both vlans created on the 3500 switch #3, Vlan2(Voice)-192.168.40.0 and Vlan1(Data)-192.168.30.0 and enabled routing on this Switch, then UNTAG port 43 (3500 switch #3) that goes to E7 (4108 switch #2) with Vlan1
and on 4108 switch #2 just add this line :
4100(config)#ip default-gateway a.b.c.d (where a.b.c.d is the Vlan1 ip address on the 3500 switch#3).
and on the 3500 swithces add to Vlan2 this command:
3500(config)#vlan 2 ip helprer-address (DHCP server ip address) --- for each switch.
on 3500 #1 & #2 switches you have to add also
3500(config)#ip default-gateway a.b.c.d (where a.b.c.d is the Vlan1 ip address on the 3500 switch#3).
Now Routing is done on the 3500 swtich#3, and 4100 switches serve the data network and PCS get their IP addresses from the DHCP server, and Voice devices get their IP from DHCP also.
Now for internet connectivity, you can use a static route on the 3500#3 points to the Internet gateway/fw:
3500(config)#ip route 0.0.0.0 0.0.0.0 192.168.30.254
And on the FW to internet add a static route to serve vlan2 :
FW(config)#ip route 0.0.0.0 0.0.0.0 a.b.c.d (where a.b.c.d is the Vlan1 ip address on the 3500 switch#3).
Don't forget to assign points.
Good Luck !!!