The D3100 is comparable to the D40, that is, upgraded with modern tech
You cannot seamlessly use a D3100 nor a d5100 with older lenses (the lenses won't autofocus, but will mount)
Better option - you might consider an 18-105 VR + 70-300 VR, or get the newer 55-300 VR and keep the 18-55 VR
Nikon D3100
70-300 VR
A few images are shown, above
Nikon d300
Nikon SB600
hand-held
Calle Lilly
Abstract
Nikon D300
Nikon 70-300 VR
Orange Slipper
One Get
Yes, I shoot with the Nikon 85mm micro
I used both lenses, yesterday, but there were times when I could not get close enough with the 85
On my website, below, I have many shots of flowers and orchids
dennisrubinphotography.zenfolio.com
Nikon D300
Nikon 70-300 VR
Nikon SB600
Benro Tripod, Slik Pistol Grip
Red, I said
White Orchid