  We determine the expected yield of detections of solar-like oscillations for
the PLATO ESA mission. We used a formulation from the literature to calculate
the probability of detection and validated it with Kepler data. We then applied
this approach to the PLATO P1 and P2 samples with the lowest noise level and
the much larger P5 sample, which has a higher noise level. We used the
information available in in the PIC 1.1.0, including the current best estimate
of the signal-to-noise ratio. We also derived relations to estimate the
uncertainties of seismically inferred stellar mass, radius and age and applied
those relations to the main sequence stars of the PLATO P1 and P2 samples with
masses equal to or below 1.2 $\rm{M}_\odot$ for which we had obtained a
positive seismic detection. We found that one can expect positive detections of
solar-like oscillations for more than 15 000 FGK stars in one single field
after a two-years run of observation. For main sequence stars with masses $\leq
1.2 \rm{M}_\odot$, we found that about 1131 stars satisfy the PLATO
requirements for the uncertainties of the seismically inferred stellar masses,
radii and ages in one single field after a two-year run of observation. The
baseline observation programme of PLATO consists in observing two fields of
similar size (in the Southern and Northern hemispheres) for two years each. The
expected seismic yields of the mission are more 30000 FGK dwarfs and subgiants
with positive detections of solar-like oscillations, enabling to achieve the
mission stellar objectives. The PLATO mission should produce a sample of
seismically extremely well characterized stars of quality equivalent to the
Kepler Legacy sample but containing a number of stars $\sim$ 80 times larger if
observing two PLATO fields for two years each. They will represent a goldmine
which will make possible significant advances in stellar modelling.
