How did you install proxychains?
Your error might indicate that variable LD_PRELOAD doesn't include correct path to libproxychains.so.3, so you might need to locate it and export the variable. This would have been very easy for you to find out with a little searching.
I installed proxychains with apt on Stretch, the file was located in /usr/lib/x86_64-linux-gnu. So:
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export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libproxychains.so.3
proxychains <stuff>
On another note, why use Tor proxy for updating your repository list / upgrading your system? Bandwidth is terrible at best, and system upgrade isn't sensitive information in any sense. Unless you're unable to access repositories without proxy, what's the point?
EDIT: The first search result actually had identical command in problem statement that you were trying to run (proxychains apt-get update). Did you even try to look for the solution yourself?