usb2 vs usb3 extension cable

You should have no issues if you use this on.

Belkin USB Extension Cable (10-Feet)
http://www.amazon.com/Belkin-USB-Extension-Cable-10-Feet/dp/B00001ZWXA

PTC - 20 Meters (64 Feet) USB 2.0 Active Extension / Repeater Cable A Male to A Female - Supports High Speed USB2.0 480 Mbps

http://www.amazon.com/PTC-Meters-Extension-Repeater-Supports/dp/B0040IASMS/ref=pd_sim_pc_13?ie=UTF8&refRID=0RZ85V1HMKQTHXQKAMZQ

I have used long cables may times, I don't think USB2/3 will matter much, more of a transmission rate, which should not be a problem.  USB 2/3 are both ideal to 5 meters,

PC's that have USB 3 ports also have USB 2 ports (or at least I haven't heard of any PC that only has USB 3 ports). USB 3 ports can be identified by their blue color.

A headseat doesn't need high speeds, so it will work fine on USB 2, or even on USB 1 ports. I doubt very much they would be specced specifically for USB 3, as that would be a waste, since USB 3 ports on PC's are usually more limited than the USB 2 counterparts, and there are still many PC's around that don't have USB 3. Just get a normal USB 2 extension, and don't use the USB 3 port of the PC for it, use that for a fast disk or USB stick.

i would buy a cable with an active repeater; they go up to 50 feet :  http://www.ebay.com/itm/50-FT-Hi-Speed-480Mbp-USB-2-0-Extension-Cable-with-Active-Repeater-U2A1-A2-50-/271033783064

usb 3 connectors on laptop are marked blue

usb 3 connectors on laptop are marked blue

I have acer aspire 7740.
i can not find blue

because my computer has no usb3, there is no need to buy usb3 cable?  Or will the usb3 cable be quicker better for usb2

It doesn't make any difference.

specific answer for me
Other answers were better for other people

thanks.