this came out from my induction hob rated 6.4kw

my oven rated 3.6kw, the wires looks like ordinary ones

the reason why the oven came with, I suspect the smaller 2.5mm wires, is because the oven cannot actually use 3.6kw at any one time. these ovens have several separate elements like top heat, bottom heat etc
and you can only use a combination of it, not all. unfortunately the manufacturer always quote "maximum power" but not "operating loads"
see the pic below -

the hob, Im more worried about.
even though it is rated 6.4kw, that is with all 3 burners going full blast which rarely happens.
further more, these hobs are unlike kettles, they dont continuously use power. they turn on and off and on again to maintain that temperature
you can see this with those ceramic cooktop, they glow on and off periodically
still i will have to see that it gets a thicker wire during installation

btw usually what size are those wires inside the 3 pin socket to the MCB?

3 rings nia 

do i need something like this