Judging from the MSP Plugin version, it looks like you recently upgraded PPM to Version 8.04 (please confirm). It's shipped with the new MSP Plugin (version 6.0.000X) that supports MSP 2010, but you need to uninstall your current (old) version of the plugin, download the new plugin installer from PPM menu, and install it.
That should solve your problem and you should be able to use it with MSP 2010.
note however that PPM 8.X is not supported anymore by HP (unless you have some special support agreement with HP), so you should consider an upgrade, preferably to 9.22.
Currently we are using 8.02 PPM version and installed MSP 2010, so when we are trying to 'Send Workplan' to project faacing the issue as 'Need to install MSP Plugin 5.0.115'.Please let me know where we can find this plugin.