Question

maximum electrons that can be accomadeted in 3d orbital

Answer 1

Number of electrons that can be accommodated in an orbital:  That depends on the orbital type.  It does not  depend on the principal quantum number N.  So 3d or 4d the number is the same.

The number of electrons in an orbital depends on the Azimutal quantum number 'l'.

s orbital :  2  = 1 pair    ,  l = 0     number = 2 (2 l+1) = 2
p orbital :  6  = 3 pairs  ,  l = 1     number =  2 (2 l + 1) = 6
d orbital   10 = 5 pairs    l = 2        number = 2 (2l + 1) = 10
f orbital :   14  = 7 pairs

Answer 2

3d can accommodate 10 electrons