I think directly this conversion is not possible as packed

decimal is used for numeric value fields only.

Since it is p(8) so the numeric value field size should be

15 or 16 as [8 can be either (n+1)/2 i.e. (15+1)/2 or ( n/2)

i.e. 16/2].

So we can say (n15 or 16) will be (P8).

Alternatively (A16 or 15)