Are you talking about the lens you have on your D3100 that you got with it that you needed to know how to zoom it, or are you talking about the lens you had on your Nikon N60?
In addition, are you talking about the Nikon 28-80mm f/3.5-5.6 AF-D or the Nikon AF Nikkor 28-80mm f/3.3-5.6G. Either of these lenses will work with your D3100, but neither lens will auto-focus with your D3100. They don't contain their own focus motor which the D3100 needs to make an auto-focus lens auto-focus.
Rebecca, you still haven't said whether the lens you are speaking about is the Nikon 28-80mm f/3.5-5.6 AF-D or the Nikon AF Nikkor 28-80mm f/3.3-5.6 G.
Assuming you are talking about one of the above lenses they won't auto-focus on the following current Nikon DSLR cameras; D3000, D3100, or D5000. They will auto-focus on other current consumer level Nikon DSLR cameras including the D90, and the D7000. They will also auto-focus on Nikon's other current cameras in the prosumer and pro lines.
Of the current Nikon DSLRs, the D3000, D3100, or D5000 will not be able to auto-focus with the lens.
Of the current Nikon DSLRs, the D90, D7000, D300s, D700 and the D3 series will be able to auto-focus with the lens.
Please note two things about this lens. First, this was a very inexpensive lens when it was manufactured. It has considerable barrel distortion at the short end and while it's a fairly sharp lens, its contrast is so-so at the lower f/settings. Second, to use this lens and have it work properly on today's DSLRs, you must set its aperture ring to f/22, its smallest aperture.