Expected number of probes in open addressing in case of an unsuccessful search = 1/(1-$\alpha$) , where $\alpha$ denotes the load factor i.e. n/m.

So 1/(1-$\alpha$) = 3

Hence, $\alpha$ = 2/3

Now, Expected number of probes in open addressing in case of an successful search = (1/$\alpha$)*ln(1/(1-$\alpha$))

Putting $\alpha$=2/3 in the above formula, we get the expected probes for successful search as 1.647.

So 1/(1-$\alpha$) = 3

Hence, $\alpha$ = 2/3

Now, Expected number of probes in open addressing in case of an successful search = (1/$\alpha$)*ln(1/(1-$\alpha$))

Putting $\alpha$=2/3 in the above formula, we get the expected probes for successful search as 1.647.