Answer:
Pleins de rêves is a French equivalent of 'full of dreams' The masculine adjective 'pleins' means 'full'. The preposition 'de' means 'of'. The masculine noun 'rêves' means 'dreams'. All together, they're pronounced 'pleh duh rehv'.
That's just one way of saying 'full of dreams' in French. It depends upon the context. The example refers to more than one person or thing that's 'full of dreams'. There are three other possibilities.
One is 'full of dreams' about one masculine person or thing. It's 'plein de rêves'. It's pronounced 'pleh duh rehv'.
Then there are the two possibilities about one or more feminine individuals or things. The phrase in the singular is 'pleine de rêves', which is pronounced 'plehn duh rehv'. The plural form is 'pleines de rêves', which is pronounced the same way.