Intelligent reflecting surface (IRS) is an emerging technology for beyond fifth-generation (B5G) networks conceived from metamaterials that enhances the communication channel through controllable passive reflecting of transmit signals. However, the IRS-assisted communication model and optimization of available resources need to be improved further from existing works. In this paper, we obtain the expression of reflection coefficient of IRS panel by exploiting the given data of radar communications. And, using the reflection coefficient, we derive the expression of received power that incorporates the free space loss, reflection loss factor, physical dimension of the IRS panel, and radiation pattern of the transmit signal. Moreover, to maximize the received power, we jointly optimize the reflective phase shift and location of the IRS panel. To obtain more pursuits, we also investigate the semi-adaptive schemes where the phase shift and location are individually optimized while keeping other at a fixed value and examine the global optimality of obtained solutions. Lastly, via obtained numerical results, we get key insights on proposed analysis and optimal solution for different schemes.