The preparation of the I 526 petition,the process of the USCIS adjudicating the I526 petition,and the individual application for the conditional permanent residency status may take up to 12 months. However this is only an estimate of time delay and can be more or less. The possession of a B1/B2 visa has no bearing on obtaining an EB-5 visa.
In order to file for adjustment of status with USCIS rather than filing for a visa abroad with the State Department, requires you to have an approved I-526 AND be in lawful non-immigrant status at time of filing the I-485 with USCIS. USCIS might or might not allow an extension of status on your B-1 IF you can justify that you are attending to legitimate business needs/concerns. If the I-526 remains pending too long and the B visa entry expires then, you may need to depart and pursue Consular Processing instead,