You can get a little box that plugs into a receptacle that you then plug power cords into. The protection is in the box at the wall receptacle.
You can get a cord with a protector at the output end of what amounts to an extension cord, and the protection is at the other end where you connect the device.
If the surge is expected to be from something on the other side of the wall, the box at the wall receptacle should prevent it from getting into any of the cords you plug into the box, but too long a cord between the protector and anything you plug into it can allow "induced surges" between the protector and the device you want protected, or surges produced by one of the plugged-ins to damage another one on the same "protected cord."
If a surge might be caused by the thing(s) you plug in at the other end of a longer cord, having the protection as close as possible to the thing you want to protect may give a quicker clamp-down, but too long a distance to a good grounding point may give it nowhere to dump the bump.
The kind that give "protection at the wall" are fairly rare here, and mostly limited to ones intended to be used with small single devices.
The ones that have a cord with the protection switching at the output end, at least the ones I've found here, seldom state a length/distance limit. The protection should be good for the length of cord they come with, but they do assume you won't plug an extension cord between the protector and the device or use an extension cord between the wall and the "protector." (They may or may not state that assumption, but it's likely to be in the fine print somewhere that gives all of the weasel-out conditions of the guarantee. You can read the fine print only if you ask them before you need to know them all.)
An additional "escape clause" they have generally is due to the fact that the protection wears out eventually, usually more affected by how many times the protection trips but also just by continual use.
The most common wear-out failure is just that the device trips and the reset won't turn it back on, but there is a decline in the size of surges that can be blocked (and/or the size of surge that would trip them) even if there's never been a surge big enough to actually shut it off. Some kinds don't have a breaker with reset button/switch, so they either just don't turn themselves back on, or they start to trip much more frequently on smaller transients.
gnu has to worry about this kind of stuff since his arc welder and the 50 HP irrigation pump are on the same protector as his computer, but for most of us its more bother than its worth. We just buy one that "looks good" and learn to say "shit happens."
While the "guarantees" on the package can be extravagent, few of them ever pay off. That likely is because we don't save the packaging and don't have any idea who to complain to when something happens - or we have so many packages we can't tell which one the device that failed came in.