It seems that you already have an older Node installed and it is in your PATH before the new Node.
Assuming that you have installed the new Node correctly, you might add its path to your PATH before the old one. For example:
PATH="/path/to/new/node/bin:$PATH"
Or you may need to install it once again in a different path in case the installation didn't go as you wanted.
An automatic way to handle Node versions would be using nvm:
but it can still get into conflicts if you have Node installed before you install nvm.
A simple way to install Node would be to decompress a binary distribution into e.g. /opt/node-7.10.0:
wget https://nodejs.org/dist/v7.10.0/node-v7.10.0-linux-x64.tar.gz
tar xzvf node-v7.10.0-linux-x64.tar.gz
sudo chown -Rv root.root node-v6.7.0-linux-x64
sudo cp -Rvi node-v7.10.0-linux-x64 /opt/node-7.10.0
or from sources:
wget https://nodejs.org/dist/v7.10.0/node-v7.10.0.tar.gz
tar xzvf node-v7.10.0.tar.gz
cd node-v7.10.0
./configure --prefix=/opt/node-7.10.0
make && make test && echo OK || echo ERROR
# If everything is ok:
sudo make install
and then using:
PATH="/opt/node-7.10.0/bin:$PATH"
See This tutorial where I explain various ways to install Node and what you need to do with the PATH afterwards. Of course you don't need the version included in the path to Node but I don't know where your old Node is installed so this example is unlikely to overwrite some other version. The path prefix could be /opt/node. With /usr/local you install along other files so you need to be extra careful - see the tutorial for details.
See also: