Number of strings? Is each particle associated with an unique string and where exactly is the string located, if it's vibration produces the appearance of a particle?
What I mean is if I see an electron, does it have an unique string corresponding to it and where is this string physically (inside the electron or somewhere else)?
 A: 
Is each particle associated with an unique string and where exactly is the string located, 

At the moment the standard model of particle physics has elementary particles as point particles. The standard model encapsulates the overwhelming majority of data gathered . Going to strings means going up to a dimension for the particle, instead of a point it will be represented by a string.

if it's vibration produces the appearance of a particle? 

The vibrations of a string theory  which will successfully  model elementary particle physics have to include the symmetries of the standard model so that it can be embedded, i.e. that one can  make a one to one correspondence of a vibrating string with a specific four momentum vector of the particles in the table.

What I mean is if I see an electron, does it have an unique string corresponding to it 

In principle in a successful string model, an electron will be a vibrating string in a model corresponding with its four vector and quantum state. Instead of a point with an accompanying four vector , it will be one dimensional with a four vector and a string vibration signature corresponding to the standard model table.

and where is this string physically (inside the electron or somewhere else)?

Where the model of a point electron is now, the further magnification shows it is a one dimensional string, once a successful string theory  becomes the standard model.
