How To Increase Fps In Sony Vegas

From Vegas Help for those 144FPS recordings you already have:

Working with high-frame-rate (HFR) clips Working with high-frame-rate (HFR) clips

If you want to use high-frame-rate clips to create slow-motion effects, you need to adjust the clip's playback rate to conform to the project's frame rate.

You can use the Project Media window to set the clip's playback rate when creating events, or you can use the Event Properties dialog to edit events already on the timeline.

Adding HFR clips from the Project Media window

Add your clips to the Project Media window. For more information, see Using the Project Media window
Click to position the cursor in the timeline where you want to create an event.
Right-click the clip in the Project Media window and choose Add at Project Frame Rate.
An event is created at the cursor position, and the event's Playback rate value is calculated to allow the event to play back using the project frame rate. For example, if you add a 120 fps clip to a project with a frame rate of 30 fps, the event's playback rate will be set to .25.
Event playback is limited to a range of .25 to 4.0x playback. If the event needs to be modified beyond that range, a velocity envelope is applied. For example, when using a 240 fps clip in a 24 fps project, the event's playback rate is set to .25, and a velocity envelope is applied to achieve the required playback rate of .1. In these cases, the event's audio will not play in sync with the video.
If you need to check or adjust your project's frame rate, you can use the Project Properties dialog. For more information, see Setting project properties

Setting the playback rate of an existing event

Right-click the clip on the timeline and choose Properties from the shortcut menu.
On the Video Event tab of the Project Properties dialog, click the Conform to Project Frame Rate button.
The event's Playback rate value is calculated to allow the event to play back using the project frame rate. For example, if you add a 120 fps clip to a project with a frame rate of 30 fps, the event's playback rate will be set to .25.
Event playback is limited to a range of .25 to 4.0x playback. If the event needs to be modified beyond that range, a velocity envelope is applied. For example, when using a 240 fps clip in a 24 fps project, the event's playback rate is set to .25, and a velocity envelope is applied to achieve the required playback rate of .1. In these cases, the event's audio will not play in sync with the video.
If you need to check or adjust your project's frame rate, you can use the Project Properties dialog. For more information, see Setting project properties
Trim the event end to adjust the event so all frames are visible. For more information, see Adjusting an event's length