VLAN Between Dell - Netgear - Cisco

For starters you can't do this without being at the site.  If it's NOT possible to travel there then hire an IT consultancy from the local area to come in there and do this.  I run an IT consultancy myself and this sort of thing would probably cost you around $400 because I would have to spend time reviewing the configs of the devices and familiarizing myself with them and figuring out what you wanted to do.  It's about a half a day project.

You might consider that since your MPLS router is Cisco, if you had purchased a Cisco Catalyst switch and a Cisco edge router instead of the Dell, and had them on Cisco support, then Cisco could help you out at no cost.  And the cool thing about Cisco devices is they have that "reload in 10" command so if you lock yourself out you wait 10 minutes and everything reloads itself to the prior configuration.   Situations like yours are one of the reasons enterprises use consistent vendor gear.  But I digress.   Anyway, explain to your boss you need plane tickets or a budget to hire a consultancy.

You didn't say if the Cisco device is owned by the Telco that is supplying the MPLS access to you.  In any case you need to know how the port's configured on it so you need the config for it.  In general I've seen these MPLS handoffs done 2 ways.  The first way is they hand you a trunking port off the Cisco and you plug another Catalyst into that then you get access to all VLANS configured on the MPLS network.  You may or may not be able to do this with the Netgear.  It may not speak Cisco trunking protocol.  The second way is if the customer does not have Cisco gear that can deal with trunking ports.  In that case the particular VLAN assigned to whatever circuit is terminating at the site is terminated in the telco-supplied Cisco and the port handed off to the customer is untagged.  If the customer wants multiple VLANS then more VLAN circuits are built in the MPLS network assigned to additional ports on the Telco-supplied Cisco and handed off untagged.  The customer can plug all those ports into their switch and handle their own internal VLANS.