Kellie Pickler’s favorite concert

(CNN) -- Kellie Pickler calls them her favorite shows.

"When you get up onstage and you look out and you see a sea of soldiers or sea of marines or just a sea of your military in general, it's just so overwhelming, and it just really makes you feel good," Pickler says.

The 26-year-old country music star has been singing for the troops as a USO volunteer since 2007. She has taken part in six USO tours to bring "a little piece of home" to servicemen and women stationed overseas, including those in Kuwait, Iraq and Afghanistan.

"I've met so many amazing people on these USO tours," Pickler says, recalling one of her most memorable moments from a Memorial Day trip to Afghanistan in 2012.

"It was myself and my band and maybe 12 other soldiers that play guitar, drums, keys," she remembers.

"We all met at the chapel on the base, and we sat there all night, I mean probably two or 2:30, three in the morning playing old Johnny Cash songs to just everything you could think of. We just had a pickin' party."

Pickler's connection to the military is deeply personal. Her grandfather, a retired Marine, helped raise her. She says she developed "a great deal of respect" for the troops growing up in a military family, which inspired her to get involved with the USO.

"[The troops] need to know that we haven't forgotten about them and what they do," she says. "And they need to know that we're back home supporting them and that we have their back because they have ours."

Pickler even tattooed three stars on her left arm as a reminder of her first few USO tours and her gratitude to those who serve. She encourages all Americans to find their own way to express their appreciation.

"Something as simple as when you pass someone in uniform in the airport or you're at Starbucks getting coffee and someone in uniform walks in, just go up and say, 'Thank you.' Shake their hand. 'Thank you for your service. Thank you for what you do. Because you do what you do, I'm able to do what I do.'"