I don't have a solar filter but I have a 10 stop, 8 stop, 4 stop and a 2 stop ND filters can I take the 10 stop + 8 stop and combine them to make a 18 stop filter or the 10 stop + 4 stop + 2 stop to make a 16 stop filter to photograph a solar eclipse and it not destroy my camera?
In theory, the 10-stop and 8-stop filter could do the job (with about 1 1/3 stop disadvantage to a solar filter). 2^(10+8) is a light reduction factor of 262,144 and solar filters usually have a factor of 100,000. Two filters are better than three here because of potential ghosting occurring from internal reflections between the filters.
However, the main danger of not using a solar filter is that you need to be sure that your ND filters are also blocking 100% of UV and infrared rays. Without protection from both UV and Infrared, you may damage your camera's sensor, let alone damage your eyes if you attempt to look through your camera's viewfinder.
Some people advocate only using live view with stacked ND filters for viewing the sun, but this is risky if you are unsure of the UV and infrared capabilities of your ND filters. You might find that a suitable alternative is to photograph indirectly using a pinhole projection or camera obscura to project the sun, and neither of these will require you to use ND filters.
Last, if you are able to view the eclipse at totality, filters are not needed during the brief window when the sun is completely blocked. But this still has the same risks, as your timing has to be precise so that you do not have your eye to the camera or your camera's sensor exposed at the moment the moon no longer covers all of the sun.