REALLY NEED HELP

Your D6200 is an AC1200 class device.  While any extender should work with it, an AC1200 class extender would be comparable.  Netgear's extenders can be found here (link).

OTOH, if your current devices cannot take advantage of it, then it may be overkill, so it would help to know what you have.

Other factors that may affect your decision include whether you can or are willing to connect the extender to your D6200 with Ethernet.  This is recommended because it allows the extender to operate as an Access Point, which is faster.  If you have devices that you want to wire into the extender, then an extender with multiple Ethernet ports may be more suitable than one with only a single port.  Finally, an extender with large antennas may have slightly better range.

Another thing you can try is look for a better location, try to place your device higher, check for interference which can be anything around such a microwave metal, concreate, doesnt matter how little or how thick wifi is very sensitive anything can cause the signal to dip.