A retro/film-style look in Lightroom usually comes from a few combined adjustments:

• Warm the white balance slightly.
• Reduce contrast and lower overall saturation.
• Lift the blacks and darken the whites so the image has softer blacks and less-bright highlights.
• Add a slight yellow tint to the color balance.
• If needed, add a little grain/noise for a more film-like feel.
• For a softer dreamy look, use a radial filter and reduce clarity and sharpness; you can repeat this in multiple areas if needed.
• Add a subtle post-crop vignette to finish the look.

Some examples of this style also use extra fill light or increased clarity to emphasize texture, though that can be overdone.

Capture choices matter too: shooting with a fast prime lens wide open can help give images the shallow-depth, classic feel often associated with this look.