c++ typdef and subclassing

I am having a bit of trouble with a c++ class that I am trying to implement.

I subclass std::vector but I can't get the iterator. Here's my sample code:

This line "MyPairList::iterator Item = this->begin();" I can't get the iterator to my template class.

How can I fix this and why exactly is it happening because right now I am totally at a loss. Also this is all described in my .h file, no .cpp file.

#include <string>
#include <unordered_map>
#include <vector>

using namespace std;

    template<typename T>
    class MyPairList : public vector<T>
    {
    public:
        void Form()
        {
            _idColl.clear();
            _nameColl.clear();


            MyPairList::iterator Item = this->begin();
            for ( ; Item != this->end() ;  ++Item)
            {
                _idColl.insert(make_pair( (*Item)->ID, (*Item) ));
                _nameColl.insert(make_pair( (*Item)->Name, (*Item) ));
            }
        }

        T Lookup(int pID)
        {
            if (_idColl.find(pID) != _idColl.end())
            {
                return _idColl[pID];
            }

            return T();
        }

        T Lookup(const string &pName)
        {
            if (_nameColl.find(pName) != _nameColl.end())
            {
                return _nameColl[pName];
            }

            return T();
        }

        MyPairList()
        {
        }

    private:
        unordered_map<int, T> _idColl;
        unordered_map<string, T> _nameColl;
    };